Philips

About: Philips is a company organization based out in Vantaa, Finland. It is known for research contribution in the topics: Signal & Layer (electronics). The organization has 68260 authors who have published 99663 publications receiving 1882329 citations. The organization is also known as: Koninklijke Philips Electronics N.V. & Royal Philips Electronics.

Electron counting model and its application to island structures on molecular-beam epitaxy grown GaAs(001) and ZnSe(001).

Abstract: The principal reconstructions found on the low-index planes of GaAs and ZnSe can be explained in terms of a simple electron counting model. A surface structure satisfies this model if it is possible to have all the dangling bonds on the electropositive element (Ga or Zn) empty and the dangling bonds on the electronegative element (As or Se) full, given the number of available electrons. This condition will necessarily result in there being no net surface charge. The justification for this model is discussed. The GaAs(001)-(2\ifmmode\times\else\texttimes\fi{}4) reconstruction is known to involve surface dimers. It is shown that a (2\ifmmode\times\else\texttimes\fi{}4) unit cell with three dimers and one dimer vacancy is the smallest unit cell that satisfies the electron counting model for this surface. The electron counting model is used to explain the structure of islands imaged by scanning tunneling microscopy on the GaAs(001)-(2\ifmmode\times\else\texttimes\fi{}4) surface. The model shows that island structures built up from complete (2\ifmmode\times\else\texttimes\fi{}4) unit cells can be stable if they extend in the 2\ifmmode\times\else\texttimes\fi{} direction, but not if they extend in the 4\ifmmode\times\else\texttimes\fi{} direction. These island structures can also provide an explanation for the different step structures seen on GaAs(001) vicinal surfaces. Much less is known experimentally about step and island structures on ZnSe(001). Structures on this surface predicted by the electron counting model differ significantly from those found on GaAs(001).

On the heat of formation of solid alloys

Abstract: We demonstrated recently that the available experimental data on the heat of formation of solid alloys of transition metals can be accounted for by means of a cellular model. The energy effect is derived from two contributions; a negative one, arising from the difference in chemical potential, ϑ∗, for electrons at the two types of atomic cells, and a second term, which reflects the discontinuity in the density of electrons, n ws , at the boundary between dissimilar atomic cells. Expressed as a formula, ΔH ~ [-Pe(Δϑ∗) 2 + Q(Δn ws ) 2 ] . In this paper we demonstrate that the second term is preferably to be written as Q 0 (Δn 1 3 ws ) 2 . Values for P and Q 0 can be derived from basic arguments. The advantage of this alteration is that the values for P and Q 0 are now nearly the same for widely different alloy systems (i.e., as different as intermetallic compounds of two transition metals, and liquid alloys of two non-transition metals). It is demonstrated that the description (and hence the predictions) for heats of formation of alloys of transition metals is sufficiently accurate to be of practical interest. The present model conflicts strongly with descriptions of heats of formation of transition metal alloys in terms of the Engel-Brewer theory.

Towards molecular electronics with large-area molecular junctions

Abstract: The use of molecular electronics is a much-discussed alternative to conventional silicon devices: the prospect of such tiny components has obvious implications for miniaturization. One approach is to replace the conventional semiconductor with a single molecular layer that self-organizes between two electrodes. Molecular tunnel junctions have been made in such systems, but they tend to be hard to reproduce, unstable and limited to small diameters. Now Akkerman et al. have developed a relatively simple way of producing stable, reproducible molecular junctions with large areas from self-assembled monolayers of alkanethiols. The process is compatible with standard integrated circuit technologies and could offer a cheap way forward in the quest for practical molecular electronics. A relatively simple method to fabricate stable, reproducible molecular junctions with large areas from self-assembled monolayers of alkanethiols has been developed — this approach could offer a cheap and promising way forward for molecular electronics. Electronic transport through single molecules has been studied extensively by academic1,2,3,4,5,6,7,8 and industrial9,10 research groups. Discrete tunnel junctions, or molecular diodes, have been reported using scanning probes11,12, break junctions13,14, metallic crossbars6 and nanopores8,15. For technological applications, molecular tunnel junctions must be reliable, stable and reproducible. The conductance per molecule, however, typically varies by many orders of magnitude5. Self-assembled monolayers (SAMs) may offer a promising route to the fabrication of reliable devices, and charge transport through SAMs of alkanethiols within nanopores is well understood, with non-resonant tunnelling dominating the transport mechanism8. Unfortunately, electrical shorts in SAMs are often formed upon vapour deposition of the top electrode16,17,18, which limits the diameter of the nanopore diodes to about 45 nm. Here we demonstrate a method to manufacture molecular junctions with diameters up to 100 µm with high yields (> 95 per cent). The junctions show excellent stability and reproducibility, and the conductance per unit area is similar to that obtained for benchmark nanopore diodes. Our technique involves processing the molecular junctions in the holes of a lithographically patterned photoresist, and then inserting a conducting polymer interlayer between the SAM and the metal top electrode. This simple approach is potentially low-cost and could pave the way for practical molecular electronics.

Combinations of genetic algorithms and neural networks: a survey of the state of the art

Abstract: Various schemes for combining genetic algorithms and neural networks have been proposed and tested in recent years, but the literature is scattered among a variety of journals, proceedings and technical reports. Activity in this area is clearly increasing. The authors provide an overview of this body of literature drawing out common themes and providing, where possible, the emerging wisdom about what seems to work and what does not. >

High voltage thin layer devices (RESURF devices)

Abstract: The application of a somewhat unusual diode structure opens the possibility to make novel kinds of high voltage devices even with very thin epitaxial or implanted layers. In the new structures crucial changes in the electric field distribution take place at or at least near the surface. The acronym RESURF (REduced SURface Field) was chosen.